1. Field of the Invention
The present invention relates to solid propellant disposal and recovery and, more particularly, to a method of recovering inorganic oxidizer salt from the waste propellant.
2. Description of the Prior Art
There is a considerable amount of waste propellant produced during the manufacture of solid propellant rocket motors, such as from the excess cast into the motor casing to compensate for shrinkage, from motors or masterbatches that do not meet specifications, as well as overage motors removed from service. Typically this waste propellant has been scrapped since the flammability and rubbery characteristics have been believed to prevent economical reclamation.
Large quantities of waste propellant have been and are now being burned in open burning pits. Due to increasing environmental pressure, many propellant producers are either now burning waste propellant and scrubbing the combustion gases or are planning on or will be required to so in the future.
The expected quantity of waste composite propellant from the U.S. Space Shuttle Solid Rocket Motor boosters from 1976 through 1989 is expected to be about 8.times.10.sup.6 lb. The cost of burning waste propellant is considerable. Economic recovery of propellant ingredients would save energy, cost, reduce materials and eliminate the costly, undesirable and hazardous open burning or incineration procedure.
A method of removing, or leaching, ammonium perchlorate (AP) from composite propellants is taught in U.S. Pat. No. 3,451,789, by Meldon McIntosh. In this process, propellant removed from rocket motors is chopped into small chunks which are leached with water. However, the tacky nature of the composite propellants results in the formation of large agglomerates of propellant which prevent the necessary intermixing of water and propellant required for efficient extraction of the oxidizer. In order to obtain more than 25 to 30% of the available oxidizer the agglomerated propellant requires continuous tearing and chopping apart under the leach solution. This requires a large expenditure in time and power to run the chopper while extracting the AP.